Major advancesin human health will come from understanding the functions of the genome. Unfortunately, many phenotypes are too variable for genetic analyses. A phenotype isthe product of both genetic and environmentalfactors, and although the genetic ones can be controlled with great precision, the environmental ones cannot. This isbecause the pertinent environmentalvariables influencing many phenotypes have not been identified. This project isfocusedon two phenotypesthat are highly variable even in inbred mice;taste preferences and diet-induced obesity. Thegoal isto assess the contribution of some early life laboratory variables to these adult phenotypes. The early variables manipulated will be (1) litter size and composition. Thehypothesis underlying this aim is that one or more factor related to the mouse's interaction with itslittermates (both in and ex utero) produces life-long effects on itsphenotype. The approach will involve comparing the adult phenotypes of mice originating from litters of different sizes and sexratios. (2) Neonatal and weaning diet. The hypothesis underlying this aim isthat uncontrolled aspects of the diet mice ingest before and during weaning influences adult phenotype variability. The approach will be to compare the phenotypes of adult mice fed various diets whenyoung. (3) Factors acting during shipping from breeder to test institution. Thehypothesisunderlying this aim isthat factors related to the transportationof mice from breeder to test site are responsible for inducing variability in adult phenotype. The approach will be (a) monitor environmental parametersduring shipping, and (b) systematically evaluate the contribution of each environmental parameter (e.g., food deprivation, water deprivation, temperature, motion)on adult phenotype. Theproposed studies will characterizesome environmental factors that may exert uncontrolled effects on adult phenotypes. The results will lead to better environmental controls in future work and, asa direct consequence, easierand more rapid progress with genetic analyses.